Referring to FIG. 1 and FIG. 2, a conventional height adjusting mechanism of a musical instrument chair includes a stand 1. The stand 1 is provided with a central rod 2, a connecting head 3, a screw rod 4, a chair cushion 5 and a fixing ring 6. The fixing ring 6 is in a hollow ring shape, where the interior of an upper segment of the fixing ring is a reducing segment 7, and threads are disposed therein and screwed with the screw rod 4. The interior of a lower segment of the fixing ring 6 is an expanding segment 8, which sleeves a top end of the connecting head 3 and is pressed against an edge face of the connecting head 3 by a radial-penetrating pressing screw 9 so as to fix the fixing ring 6. When the height is adjusted, the pressing screw 9 is unlocked, and then the height of the chair cushion 5 is adjusted in a manner of rotating the screw rod 4. However, the screwing adjustment manner is slow, and cannot meet demands for use.
Also as shown in U.S. Pat. No. 5,927,810, an adjusting rod fixing structure of a musical instrument chair is disclosed. A screw rod can be maintained at a fixed height without shaking, and can be finely adjusted in a stepless manner. However, the structure is complicated and the assembly cost is high; moreover, the screw rod is still fixed in a screwing manner; in case of excessively screwing it down, a weak user cannot make it loosened; and in case of not screwing it down, a danger may be caused due to unexpected loosening.